1. Technical Field
The present invention relates to a package and a vibrating device having a vibrating reed housed in the package.
2. Related Art
As a clock source or the like of an electronic circuit of various electronic apparatuses such as information and telecommunications equipment, office automation equipment including computers, or consumer equipment, a vibrating device having a vibrating reed bonded and tightly sealed in a package has been widely used. Especially in recent years, with a growing need for a smaller and thinner electronic apparatus, a further smaller and thinner vibrating device is required. In addition, many surface mount package type vibrating devices suitable for mounting on a circuit board of an electronic apparatus have been adopted (refer to JP-A-2005-241380, for example).
A piezoelectric device (hereinafter referred to as vibrating device) disclosed in JP-A-2005-241380 has a package (hereinafter referred to as package base) having a concave portion formed by stacking, on flat plate-like base substrates (first and second substrates) obtained by shaping base materials such as green sheets for example, a frame-like substrate (third substrate), and then firing them, and a piezoelectric vibrating reed (hereinafter referred to as vibrating reed) housed in the concave portion of the package base. The vibrating reed is positioned on mount electrodes (electrode portions) disposed in the concave portion of the package base and bonded thereto with a bonding member such as a conductive adhesive, thereby being electrically connected thereto.
A lid (lid member) is bonded to an open upper end of the package base to form the package, and the vibrating reed is housed in an internal space (cavity) of the package formed by closing the concave portion with the lid.
In the bottom of the package, a through hole communicating between the internal space and the outside is formed. The through hole includes a large hole on the outside side and a small hole on the internal space side formed in a concentric fashion in communication with each other. Because of the difference in size of the opening shape, a step portion is formed at an intermediate part of the through hole.
A sealing (hole sealing) process for the vibrating device is carried out by placing the package inside a vacuum chamber or the like, for example. Specifically, outgas remained inside the package is first discharged to the outside through the through hole by drawing a vacuum.
Next, by a method of, for example, irradiating a sealing member formed of a spherical metal arranged on the step portion of the through hole with a laser beam, the sealing member is melted to close the through hole, so that the vibrating reed bonded in the package is tightly sealed in a favorable state where a noxious outgas is removed from the internal space.
However, in the vibrating device disclosed in JP-A-2005-241380, since the through hole is disposed in the package for removing the gas and sealing the hole, the mechanical strength is reduced. Therefore, due to pressure applied when depressurizing the internal space in the sealing process for the vibrating device, or impacts such as dropping, there is a problem that, for example, a crack starting from the through hole may occur in the package. Especially in view of achieving a reduction in size of the package, the mechanical strength may be remarkably reduced.